SR04 is a small mobile robot suitable for exploring human habitats unattended. It is controlled by a Motorola HC6811 microprocessor running in an M.I.T. 6.270 CPU card, similar to the commercially available "Handy Board." Two 12-volt DC gear-head motors maneuver the robot in a dual-differential drive configuration, balanced by a non-driven tail wheel caster and powered by a 12 volt 2.2 amp-hour sealed lead acid battery. Sensory input is provided by (in order of priority): front bumper switches, IR collision avoidance, stereo sonar ranging, photo detectors, passive IR motion detection, and shaft-encoder odometry.

This is my fourth robot project, the prior three were constructed with Lego Techniques ® and variously controlled by analog hardware, a New Micros HC6811 Forth CPU, and the "Rug Warrior" CPU card sold in conjunction with Flynn’s excellent "Mobile Robots" book. This design has evolved from those robots and from many long conversations with friend and veteran robot builder Duane Gustavus.